Auditory enhancement under simultaneous masking in normal-hearing and hearing-impaired listeners

Abstract

Auditory enhancement, where a target sound within a masker is rendered more audible by the prior presentation of the masker alone, may play an important role in auditory perception under variable everyday acoustic conditions. Cochlear hearing loss may reduce enhancement effects, potentially contributing to the difficulties experienced by hearing-impaired (HI) individuals in noisy and reverberant environments. However, it remains unknown whether, and by how much, enhancement under simultaneous masking is reduced in HI listeners. Enhancement of a pure tone under simultaneous masking with a multi-tone masker was measured in HI listeners and age-matched normal-hearing (NH) listeners as function of the spectral notch width of the masker, using stimuli at equal sensation levels as well as at equal sound pressure levels, but with the stimuli presented in noise to the NH listeners to maintain the equal sensation level between listener groups. The results showed that HI listeners exhibited some enhancement in all conditions. However, even when conditions were made as comparable as possible, in terms of effective spectral notch width and presentation level, the enhancement effect in HI listeners under simultaneous masking was reduced relative to that observed in NH listeners.

Neural correlates of masked and unmasked tones: psychoacoustics and late auditory evoked potentials (LAEPs)

“…Similar to the paradigm used in this study, various psychophysical and neural phenomena have shown the influence of preceding signals on the following target tone perception, termed as “auditory enhancement” (e.g. Nelson and Young, 2010; Kreft et al, 2018). In these studies, the preceding maskers were broadband noise with a spectral notch around the target signal.…”

“…The underlying mechanism of “auditory enhancement” has been attributed to the adaptation at both low- and high-level auditory processing. For supporting the adaptation at low-level auditory processing, Kreft et al (2018) suggested that olivocochlear efferents may induce the adaptation effect in a longer time scale than the auditory nerve fibers (Guinan Jr, 2006). If this is the case, how modulation patterns (e.g., RR, RC, CC , and FC ) result in different degrees of CMR reduction is in question.…”

Spectral contrast effects and auditory enhancement under normal and impaired hearing

“…One interesting finding is that enhancement is observed under simultaneous masking, but not under forward masking for both cochlear-implant users [18] and hearing-impaired listeners [19,20]. This intriguing difference suggests a potential difference in mechanism underlying enhancement in simultaneous vs. forward masking, which has yet to be fully elucidated.…”

“…Auditory Enhancement Two recent studies in our lab have explored auditory enhancement in both cochlear-implant users [18] and listeners with sensorineural hearing loss of presumed cochlear origin [19]. In both cases, detection thresholds for a pure tone in the presence of spectrally flanking masker tones were reduced by the introduction of a precursor that was a copy of the masker.…”

A notched-noise precursor affects both diotic and dichotic notched-noise masking

“…The enhancement effect is distinct from the effect measured in the current study. The enhancement effect (e.g., [58]) refers to the increased audibility of a given target signal component of a spectral complex by prior exposure to the spectral complex with the target signal component deleted; this is suggested to be due to an increase in gain in the (neutrally) unadapted frequency region (adaptation inhibition). The latter example refers to enhancement in the case of a single unmasked target tone.…”